DE112017000494T5 - Capacitive occupant classification sensor with load-dependent antenna range - Google Patents

Abstract

A capacitive sensor element (130) of a vehicle seat occupant detection and classification device (18) comprises a first electrically conductive antenna element (132) and at least one second electrically conductive antenna element (134) connected without galvanic connection to each other adjacent to the first electrically conductive antenna element (132 ) is arranged. At least one electrically conductive bridging member (146) is fixedly attached to at least one resilient spacer (148) having resilient mechanical properties in a specified direction (54). If a mechanical load (F) in the specified direction (54) is applied to the capacitive sensor element (130) which is equal to or greater than a predetermined value for the mechanical load (F), the at least one electrically conductive bridging element (FIG. 146) provides at least one galvanic contact between the first electrically conductive antenna element (132) and the second electrically conductive antenna element (134).

Description

Technical area

The present invention generally relates to a capacitive sensor element of a vehicle seat occupant detection and classification device, a vehicle seat occupant detection and classification device comprising such a capacitive sensor element, and a vehicle seat including such a vehicle seat occupant detection and classification device.

Background of the invention

The use of vehicle seat occupancy detection systems is now widely used in vehicles, particularly passenger cars, to provide a seat occupancy signal to various devices, for example, for the purpose of a Seat Belt Reminder (SBR) or an auxiliary restraint system activation control. ARS). Seat occupancy detection systems include seat occupancy sensors, which are known to exist in a number of variations, e.g. B. based on capacitive sensing, feeling the deformation or on the feel of pressure / force. In order to meet requirements for ease of integration and field capability, weight-sensitive seat occupancy sensors have typically been placed on the B-surface of a vehicle seat, i. H. between a foam body of a seat cushion and a seat shell or cushion support springs of the vehicle seat.

Further, vehicle seat occupancy detection systems are known to be used as a means of assessing a potential activation of an installed passenger restraint system in the vehicle, such as an air bag.

Capacitive detection systems for vehicles with capacitive sensors operating in charge mode are also used for the purpose of detecting a vehicle seat occupancy. The capacitive sensors can be designed as capacitive measuring sensors without a protective electrode with a single sensing electrode. Alternatively, they may be embodied as capacitive protection sensing sensors having a sensing electrode and a guard electrode disposed proximally and isolated from each other.

It is also known in the art to combine capacitive sensors and weight sensitive sensors in vehicle seat occupancy detection systems.

For example, the patent describes US Pat. No. 7,180,306 B2 an occupant detection system comprising a weight sensor and an electric field sensor, each operatively coupled to a seat. The electric field sensor generates an electric field from at least one electrode in the bottom of the seat, provides a response to the influence of the occupant, and is capable of distinguishing the response to the condition of a sitting toddler or child from a different sitting condition. If a weight reading from the weight sensor is below a threshold, or if a child's sitting condition is detected by the electric field sensor, a signal processor provides for disabling an associated restraining actuator. The electric field sensor may include a plurality of electrodes across a first and a second region in different proximity to a sitting toddler or child, or at least one electrode in cooperation with a shield or void over at least one of the regions.

Another occupant detection device with combined sensors for detecting a seated in the passenger seat of a vehicle occupant is in the patent application US 2002/0038947 A1 described. The occupant detection device includes a plurality of electric field sensors provided in a lower part and a rear part of the seat, and a mechanical load sensor and an acceleration sensor. The electric field sensors are connected to a control unit comprising a high-frequency oscillator, a resistor, a voltage buffer and a detector. Antenna electrodes are selected by the selectors and connected between the resistor and a voltage buffer. An analog-to-digital converter performs an analog-to-digital conversion on output signals of the selected electric field sensors. Digital output signals of the electric field sensors, the mechanical load sensor and the acceleration sensor are connected to a central unit which determines a seat occupancy according to predetermined criteria based on the sensor output signals.

In another solution of the prior art disclosed in the document EP 2 062 789 A1 1, a vehicle seat occupant detection system combines a capacity based occupancy sensor and a weight based occupancy sensor. The capacitance-based sensor includes an antenna array and provides an occupancy signal corresponding to occupancy of the seat by an adult. The weight-based occupancy sensor is a shift sensor integrated within the capacitance-based sensor antenna assembly. The shift sensor also provides an occupancy signal in the Case of occupancy of the vehicle seat by an adult. The occupant detection system further includes a controller that sends an error message when the weight-based sensor, rather than the capacity-based sensor, detects occupancy.

A disadvantage of using vehicle seat occupant detection and classification devices based solely on capacitive sensing elements is the inability to correctly classify seat occupancy when vehicle grounded objects, such as an electrical device, are connected to the vehicle ground via a charging cable or a child restraint seat (CRS such as ISOFIX) grounded by hooks mechanically connected to a vehicle body is placed on the seat. The vehicle seat occupant detection and classification apparatus is based on measurements of a physical quantity, for example, an electric current through the capacitive sensor element or a complex impedance or a transmittance of the capacitive sensor element, wherein the physical quantity for an electric field between the capacitive sensor and the Vehicle body is standing. The vehicle body is electrically connected to a vehicle ground. The capacitive sensor element may be positioned on or within the vehicle seat. A seat occupant or an object placed on the vehicle seat modifies the electric field, resulting in a change in the physical quantity. In this way, an article that is grounded may result in misclassification by the vehicle seat occupant detection and classification device due to a relatively small distance between the capacitive sensing element and the grounded object.

Vehicle seat occupant detection and classification devices based on mechanical load sensors may perform well in the presence of an ISOFIX CRS or a grounded electrical device. These items do not add weight to the seat. Compared to load-based resistance measurement, capacitive sensing has the advantages of easier wiring and stable and reproducible measurement over a full temperature range as specified in typical vehicle requirements.

The need to use mechanical load sensors to close the information gap described above increases the hardware cost, complexity, and cost of such vehicle seat occupancy and classification devices.

Object of the invention

It is therefore desirable to provide a vehicle seat occupant detection system capable of reliably and correctly classifying seat occupancy without the disadvantages described above.

General description of the invention

• - ein erstes elektrisch leitendes Antennenelement, das elektrisch an eine Kapazitäts-Messschaltung zur Bestimmung einer Kapazität des kapazitiven Sensorelements anschließbar ist,
• - wenigstens ein zweites elektrisch leitendes Antennenelement, das ohne galvanische Verbindung miteinander angrenzend an das erste elektrisch leitende Antennenelement angeordnet ist,
• - wenigstens ein elektrisch leitendes Überbrückungselement, das so angeordnet ist, dass es in einer spezifizierten Richtung teilweise das erste elektrisch leitende Antennenelement und das zweite elektrisch leitende Antennenelement überlappt, und
• - wenigstens ein elastisches Abstandselement, das zumindest in der spezifizierten Richtung elastische mechanische Eigenschaften aufweist.

According to one aspect of the present invention, the object is achieved by a capacitive sensor element of a vehicle seat occupant recognition and classification device, wherein the capacitive sensor element comprises:

• a first electrically conductive antenna element that can be electrically connected to a capacitance measuring circuit for determining a capacitance of the capacitive sensor element,
• at least one second electrically conductive antenna element, which is arranged without galvanic connection to one another adjacent to the first electrically conductive antenna element,
• at least one electrically conductive bridging element arranged so as to partly overlap the first electrically conductive antenna element and the second electrically conductive antenna element in a specified direction, and
• - At least one elastic spacer element, which has elastic mechanical properties at least in the specified direction.

The at least one electrically conductive bridging element is fixedly attached to the at least one elastic spacer element. The first electrically conductive antenna element and the second electrically conductive antenna element remain galvanically separated from each other when a mechanical load smaller than a predetermined value for the mechanical load is applied to the capacitive sensor element in the specified direction.

Further, the at least one electrically-conductive bypass element provides at least galvanic contact between the first electrically-conductive antenna element and the second electrically-conductive antenna element when a mechanical load equal to or greater than the predetermined value for the mechanical load is in the specified direction is applied to the capacitive sensor element.

The term "overlap in one direction" as used in this application is understood to be an overlap of two objects as viewed in this direction.

The seat occupant classification may include at least two classes selected from a group consisting of "empty,""child," and "adult."

The term "electrically connectable" as used in this application is to be understood to include galvanic electrical connections as well as connections made by capacitive and / or inductive electromagnetic coupling. The term "galvanic contact" as used in this application is to be understood in particular as an electrical contact which can conduct a direct current (DC). In the same sense, the term "electrically isolated" as used in this application is understood to mean, in particular, that it does not conduct direct current (DC) between galvanically isolated objects.

The term "elastic" as used in this application is to be understood in particular as the property of exhibiting a reversible deformation when an external force is applied, and it is intended to provide a reversible deformation according to a linear and non-linear stress-strain Include behavior such as rubber or rubber.

The term "firmly attached" as used in this application is understood in particular to mean that an object moves in the same way as a moving object fixedly attached to it, and vice versa.

It is noted that the terms "first (r)", "second (r)", etc. are used for purposes of distinction only and are not intended to indicate or anticipate any order or priority.

The predetermined value for the mechanical load may be selected such that an adult seat occupant causes the at least one electrically conductive bridging element to provide galvanic contact between the first electrically conductive antenna element and the second electrically conductive antenna element. As a result, an entire sensitive antenna element area is increased, which leads to a larger measured value of the capacitance measuring circuit.

An electrical device placed on the seat cushion and connected to vehicle ground does not cause the at least one electrically conductive bypass element to provide galvanic contact between the first electrically conductive antenna element and the second electrically conductive antenna element. Similarly, by properly placing the bridging elements, an ISOFIX CRS will not initiate the bridging elements because of the low weight distribution of the CRS. As a result, the entire sensitive antenna element area is then that of the first electrically conductive antenna element, which leads to a smaller measured value of the capacitance measuring circuit.

Because of the force dependent sensitive antenna element area, therefore, the capacitive sensor element allows to distinguish between an adult seat occupant and, for example, an electrical device connected to the vehicle mass or an ISOFIX CRS placed on the seat cushion.

The invention is based on the recognition that grounded electrical devices and an ISOFIX CRS could result in a high capacitance value, but always have a low weight distribution, i. H. low levels of surface pressure applied to the capacitive sensing element. Strapped CRS are usually not connected to ground and therefore have low capacity values. But these strapped CRS could lead to high surface pressures. That is, a strapped CRS may cause the at least one electrically conductive bypass element to provide galvanic contact between the first electrically conductive antenna element and the second electrically conductive antenna element. However, this is not problematic due to the low capacitance values. Large capacity values in combination with high surface pressure values are only found in adult seat occupants. These criteria are used to allow the desired distinction of seat occupancy. The capacitive measurement is concentrated on areas of high surface pressure and there is no need to detect the mechanical load and capacitance independently.

A wide variety of capacitance sensing circuits for determining the capacitance of the capacitive sensing element are known in the art and therefore will not be described in detail herein. Any capacitance sensing circuit that appears appropriate to those skilled in the art may be used.

The term "determining a capacitance" as used in this application is to be understood to include an absolute measurement of a capacitance value as well as a measurement of a capacitance value relative to an arbitrarily determined capacitance zero.

Preferably, the at least one capacitive sensor is operated in the charging mode. The term "Charge mode" as used in this application is to be understood in particular as a mode for measuring a displacement current caused by the presence of a grounded object in the vicinity of a single sensing electrode (see FIG. J. Smith et al., Electric field sensing for graphical interfaces, IEEE Comput. Graph. Appl., 18 (3): 54-60, 1998 ). In general, it is also contemplated to operate the at least one capacitive sensor in transmit mode or in parallel mode in some embodiments. These two modes are also described in the aforementioned article, which is incorporated herein by reference.

In a preferred embodiment of the capacitive sensing element, at least one of the first electrically conductive antenna element and the second electrically conductive antenna element has a planar shape and is disposed and mounted on a planar surface of an electrically insulating support member. In this way, a simple shape of the capacitive sensor element can be achieved.

If at least one of the first electrically conductive antenna element and the second electrically conductive antenna element is formed as an electrically conductive strip fixedly mounted on a surface of an electrically insulating substrate, a reliable and cost effective embodiment of the capacitive sensor element with low manufacturing tolerance margins can be provided.

In some embodiments, the electrically insulating substrate may be formed by a printed circuit substrate, and the first electrically conductive antenna element and the second electrically conductive antenna element are made of conductive layers, e.g. For example, metal layers are formed which are laminated to the printed circuit substrate using, for example, an etching process. In other embodiments, the electrically insulating substrate may be formed by a polymer sheet or foil, and the first electrically conductive antenna element and the second electrically conductive antenna element are formed of a conductive material, e.g. A conductive graphite material or a metal or a conductive polymer deposited or printed on the substrate.

In another preferred embodiment of the capacitive sensing element, a region enclosed by the second electrically conductive antenna element comprises a region enclosed by the first electrically conductive antenna element. The term "object-enclosed area" as used in this application is to be understood in particular as an area of the smallest regular quadrilateral that completely covers the object in the specified direction. In this way, a compact shape of the capacitive sensor element can be achieved.

In yet another preferred embodiment, the capacitive sensor element further comprises a third electrically conductive antenna element, which is disposed adjacent without galvanic connection to the first electrically conductive antenna element and the second electrically conductive antenna element.

The first electrically conductive antenna element forms a single loop. A region enclosed by the second electrically conductive antenna element includes a region enclosed by the first electrically conductive antenna element. A region enclosed by the first electrically conductive antenna element includes a region enclosed by the third electrically conductive antenna element.

The first electrically conductive antenna element and the third electrically conductive antenna element remain galvanically separated from each other when a mechanical load which is below a predetermined value for the mechanical load is applied to the capacitive sensor element in the specified direction.

The at least one electrically conductive bridging element provides at least one of galvanic connection / galvanic contact between the first electrically conductive antenna element and the third electrically conductive antenna element when a mechanical load equal to or greater than the predetermined value for the mechanical load the specified direction is applied to the capacitive sensor element. In this way, a very compact shape of the capacitive sensing element can be achieved with a large difference between an entire sensitive antenna area at an applied mechanical load below the predetermined value and an entire sensitive antenna area at an applied mechanical load equal to or greater than the predetermined value.

In some embodiments, the single loop formed by the first antenna element may have an elliptical, in particular circular shape, or it may have a rectangular, in particular square shape.

• - mehrere zweite elektrisch leitende Antennenelemente, die in einer Ebene angeordnet sind und angrenzend an das erste elektrisch leitende Antennenelement ohne galvanische Verbindung miteinander und ohne galvanische Verbindung zum ersten elektrisch leitenden Antennenelement angeordnet sind,
• - mehrere elektrisch leitende Überbrückungselemente, die jeweils so angeordnet sind, dass sie teilweise das erste elektrisch leitende Antennenelement und zumindest eines von den zweiten elektrisch leitenden Antennenelementen in der spezifizierten Richtung überlappen, und
• - mehrere elastische Abstandselemente, die zumindest in der spezifizierten Richtung elastische mechanische Eigenschaften aufweisen.

In a further preferred embodiment, the capacitive sensor element comprises

• - a plurality of second electrically conductive antenna elements, which are arranged in a plane and are arranged adjacent to the first electrically conductive antenna element without galvanic connection with one another and without galvanic connection to the first electrically conductive antenna element,
• - A plurality of electrically conductive bridging elements, each arranged so that they partially overlap the first electrically conductive antenna element and at least one of the second electrically conductive antenna elements in the specified direction, and
• - Several elastic spacer elements, which have elastic mechanical properties at least in the specified direction.

Each of the plurality of electrically conductive bridging elements is fixedly attached to one of the plurality of elastic spacers.

The first electrically conductive antenna element and a specific one of the plurality of second electrically conductive antenna elements partially overlapped by a specific one of the plurality of electrically conductive bridging elements remain galvanically separated from each other when a mechanical load smaller than a specific predetermined value for the mechanical one Load is applied in the specified direction to the specific one of the plurality of elastic spacers to which the specific one of the plurality of electrically conductive bridging members is fixedly mounted.

The specific one of the plurality of electrically conductive bypass elements provides at least galvanic contact between the first electrically conductive antenna element and the specific one of the plurality of second electrically conductive antenna elements that partially overlaps it when a mechanical load equal to or greater than the specific one predetermined value for the mechanical load in the specified direction to the specific one of the plurality of elastic spacers, to which the specific one of the plurality of electrically conductive bridging elements is fixedly mounted, is applied.

In this way, the capacitive measurement is concentrated on areas of high surface pressure. It is unnecessary to independently measure the applied mechanical load and capacitance to avoid misclassification of objects such as ISOFIX CRS and electronic devices connected to ground. It should be noted that depending on the configuration and arrangement of the plurality of second electrically conductive antenna elements and the corresponding bridging elements, a CRS could activate some of the secondary antenna elements, but will never activate all the bridging elements.

The advantage of this system is as follows: CRS have either a high weight distribution or a high capacity. Strapped CRS are not normally connected to ground, so they have a low capacity. However, they are heavy and activate some or all of the bridging elements. ISOFIX CRS can have a high capacity due to grounding, but they are fastened by the ISOFIX hooks, so they have a low weight distribution and bridging only by very few bridging elements. Thus, the sensitivity of the capacitive sensing element is automatically tuned by the activation of the bridging elements, thus allowing discrimination between adult seat occupants and ISOFIX CRS seats.

In some preferred embodiments, the capacitive sensing element further comprises an electrically conductive guard electrode disposed proximate the first electrically conductive antenna element, the second electrically conductive antenna element or the plurality of second electrically conductive antenna elements and, if applicable, the third electrically conductive antenna element and galvanically therefrom is isolated. The electrically conductive protection electrode substantially overlaps in the specified direction the region enclosed by one of the first electrically conductive antenna element, the second electrically conductive antenna element or the plurality of second electrically conductive antenna elements and, if applicable, the third electrically conductive antenna element.

In this way, a capacitive sensor element can be provided, which can be used as a capacitive protection sensing sensor element. The technique of "protection" is well known in the art and is often used for deliberately masking and thus shaping a sensitivity state of a capacitive sensing element. For this purpose, the capacitance measuring circuit is designed to hold the protective electrode at the same electrical potential as the first electrically conductive antenna element.

According to another aspect of the invention, there is provided a vehicle seat occupant detection and classification apparatus including at least one embodiment of the disclosed capacitive sensing element, a capacitance measuring circuit for determining a vehicle occupant Capacitance of the capacitive sensing element and an evaluation unit configured to receive an output signal from the capacitance measuring circuit and to provide a seat occupant classification based on a level of the received output signal and at least a predetermined threshold value of the output signal.

In this way, the advantages provided by the disclosed capacitive sensing element also apply to the vehicle seat occupant detection and classification device.

According to another aspect of the invention, there is provided a vehicle seat comprising a seat structure for erecting the vehicle seat on a passenger compartment floor of the vehicle, a seat cushion having at least a seat foam member, a seat base supported by the seat structure, and adapted to receive the seat cushion wherein the seat base and seat cushion are adapted to support a buttocks of a seat occupant, a seat back intended to support a back of the seat occupant, and an embodiment of the disclosed vehicle seat occupant detection and classification system.

In this way, the advantages provided by the disclosed capacitive sensor element also apply to the vehicle seat.

list of figures

• 1 in einer kombinierten Perspektiv- und teilweisen Explosionsansicht schematisch einen Fahrzeugsitz und eine Fahrzeugsitz-Insassenerkennungs- und Klassifizierungsvorrichtung zeigt, die ein kapazitives Sensorelement gemäß der Erfindung umfasst;
• 2 schematisch Einzelheiten des kapazitiven Sensorelements gemäß 1 in einer Explosionsansicht zeigt;
• 3a eine schematische Draufsicht des kapazitiven Sensorelements gemäß den 1 und 2 in einem mechanisch unbelasteten Zustand ist,
• 3b eine schematische Querschnittsansicht eines Ausschnitts des kapazitiven Sensorelements in dem mechanisch unbelasteten Zustand ist,
• 4a eine schematische Draufsicht des kapazitiven Sensorelements gemäß den 1 und 2 in einem Zustand des Aufbringens einer mechanischen Kraft, die größer als ein vorbestimmter Wert ist, ist,
• 4b eine schematische Querschnittsansicht des Ausschnitts des kapazitiven Sensorelements in dem Zustand des Aufbringens einer mechanischen Kraft, die größer als der vorbestimmte Wert ist, ist,
• 5 eine schematische Draufsicht einer alternativen Ausführungsform eines kapazitiven Sensorelements gemäß der Erfindung ist,
• 6 Fühlteile der alternativen Ausführungsform des kapazitiven Sensorelements gemäß 5 in drei verschiedenen mechanischen Lastsituationen veranschaulicht,
• 7 die Aktivierung der Fühlteile des kapazitiven Sensorelements gemäß 5 für einen von einem ISOFIX CRS belegten Sitz veranschaulicht, und
• 8 die Aktivierung der Fühlteile des kapazitiven Sensorelements gemäß 5 für einen von einem angeschnallten CRS belegten Sitz veranschaulicht.

Further details and advantages of the present invention will become apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which:

• 1 in a combined perspective and partial exploded view schematically shows a vehicle seat and a vehicle seat occupant recognition and classification device comprising a capacitive sensor element according to the invention;
• 2 schematically details of the capacitive sensor element according to 1 in an exploded view;
• 3a a schematic plan view of the capacitive sensor element according to the 1 and 2 is in a mechanically unloaded state,
• 3b FIG. 2 is a schematic cross-sectional view of a section of the capacitive sensor element in the mechanically unloaded state; FIG.
• 4a a schematic plan view of the capacitive sensor element according to the 1 and 2 in a state of applying a mechanical force greater than a predetermined value,
• 4b a schematic cross-sectional view of the section of the capacitive sensor element in the state of applying a mechanical force that is greater than the predetermined value,
• 5 is a schematic plan view of an alternative embodiment of a capacitive sensor element according to the invention,
• 6 Sensing parts of the alternative embodiment of the capacitive sensor element according to 5 illustrated in three different mechanical load situations,
• 7 the activation of the sensing parts of the capacitive sensor element according to 5 for a seat occupied by an ISOFIX CRS, and
• 8th the activation of the sensing parts of the capacitive sensor element according to 5 for a seat occupied by a strapped CRS.

Description of preferred embodiments

Embodiments of capacitive sensing elements according to the invention will now be disclosed. The individual embodiments will be described with reference to a particular figure and are indicated by a prefixed number of the particular embodiment. Features whose function is the same or basically the same in all embodiments are identified by reference numerals formed from the prefixed number of the embodiment to which it refers, followed by the number of the feature. If a feature of an embodiment is not described in the corresponding description of the figure, or a reference numeral mentioned in a description of the figure is not shown in the figure itself, reference is made instead to the description of a preceding embodiment.

1 schematically illustrates (not to scale) a vehicle seat 10 with an installed vehicle seat occupant detection and classification device 18 , which is a capacitive sensor element 130 according to the invention, in a combined perspective and partial exploded view.

The vehicle seat 10 is formed by a seat of a passenger car and includes a seat structure (not shown) by which it is erected on a passenger compartment floor of the passenger car, as is well known in the art. The vehicle seat 10 further includes a seat base supported by the seat structure and configured to seat a seat cushion 12 to accommodate the seat occupant comfort. The seat cushion 12 of the vehicle seat 10 comprises a seat foam element and a fabric cover, which in 1 is omitted. The seat base and the seat cushion 12 are intended for supporting a buttocks of the seat occupant. A backrest 16 of the vehicle seat 10 is intended for supporting a back of the seat occupant.

The seat cushion 12 includes an upper surface (A-surface 14 ) and a bottom surface (B surface). The seat base has an upper surface for receiving the seat cushion 12 so that the B-surface of the seat cushion 12 is in mechanical contact with the upper surface of the seat base. A rear edge of the seat cushion 12 is proximal to the backrest 16 , and a front edge of the seat cushion 12 , which is intended to support a lower leg portion of an adult seat occupant, is distal to the backrest 16 ,

The vehicle seat occupant detection and classification device 18 includes the capacitive sensor element 130, a capacitance measuring circuit 20 for determining a capacitance of the capacitive sensor element 130 and an evaluation unit 26 , The capacitive sensor element 130 is located on the A-surface 14 of the seat cushion 12 under the fabric cover. The capacitance measuring circuit 20 and the evaluation unit 26 are in the vehicle from the vehicle seat 10 remotely installed.

The capacitance measuring circuit 20 includes a signal generation unit 22 for generating a periodic time-dependent signal indicative of the capacitive sensor element 130 is to be applied, and a sensing circuit 24 for sensing a physical quantity that is a capacitance of the capacitive sensing element 130 displays.

The evaluation unit 26 is designed to receive an output signal from the capacitance measuring circuit 20 to receive the capacitance of the capacitive sensor element 130 is indicative of an input signal and is configured to provide seat occupant classification based on a level of the received input signal and two distinct predetermined threshold values for the input signal. The seat occupant classification includes the occupancy classes "empty", "child" and "adult". The evaluation unit 26 is further configured to provide an output signal 28 to generate a seat occupancy classification. That of the evaluation unit 26 generated output signal 28 is used for the purpose of airbag activation control via a CAN communication link 56 an airbag control unit 58 supplied to the vehicle. For example, if the transmitted output signal 28 the occupancy class "adult" represents an airbag of the vehicle seat 10 used.

Well with respect to the 2 . 3a and 3b includes the capacitive sensor element 130 a first electrically conductive antenna element 132 , a second electrically conductive antenna element 134 and a third electrically conductive antenna element 136 , The first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 have a planar design and are on a planar surface of an electrically insulating support element 138 arranged and attached to this.

The first electrically conductive antenna element 132 is formed by a (compared to a lateral extent of the electrically conductive antenna element) narrow metal strip which is formed as a single rectangular loop and two terminals 144 at the ends of the loop, through which it connects electrically to the capacitance measuring circuit 20 connected. The second electrically conductive antenna element 134 is formed as a U-shaped metal strip and so adjacent to the first electrically conductive antenna element 132 arranged that the open side of the U to the two terminals 144 of the first electrically conductive antenna element 132 has. The third electrically conductive antenna element 136 is formed as a rectangular piece of sheet metal, which is adjacent both to the first electrically conductive antenna element 132 as well as the second electrically conductive antenna element 134 is arranged so that the single loop of the first electrically conductive antenna element 132 almost completely the third electrically conductive antenna element 136 surrounds, and the rectangular piece of sheet metal, which is the third electrically conductive antenna element 136 forms, within the U-shape of the second electrically conductive antenna element 134 is arranged.

Thus, an area formed by the second electrically conductive antenna element 134 is enclosed, a region of the first electrically conductive antenna element 132 in turn, which in turn comprises a region which is of the third electrically conductive antenna element 136 is enclosed, resulting in a compact installation surface of the capacitive sensor element 130 leads.

As it's best from the 3a and 3b can be seen, include the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 no galvanic connection with each other.

The first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 be easily by applying an electrically conductive material to an upper surface 140 the electrically insulating carrier element 138 formed as an electrically insulating substrate, which is designed as a polyethylene terephthalate (PET) layer. The bottom surface of the electrically insulating carrier element 138 is equipped with an electrically conductive layer which is mounted on the PET layer and designed as a protective electrode 142 to serve. The electrically conductive material of the antenna elements and / or the guard electrode, z. As a metal or a graphite material or an electrically conductive polymer, z. By printing, deposition, laminating or any other suitable deposition technique on the substrate.

The protection electrode 142 is disposed proximally and from the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 isolated. The electrically conductive protection electrode 142 overlaps in a specified direction 54 Towards the upper surface 140 the electrically insulating carrier element 138 and disposed perpendicularly to it, substantially the region of one of the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 is enclosed.

In addition, the capacitive sensor element comprises 130 four electrically conductive bridging elements 146 , which are respectively arranged to be the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 in the specified direction 154 partially overlap.

For this purpose, each of the electrically conductive bridging elements 146 is formed as a circular metal ring which is opposite to the specified direction with respect to a direction 54 over a corner of the four corners of the single electrically conductive loop of the first electrically conductive antenna element 132 is arranged. Each of the electrically conductive bridging elements 146 is firmly attached to one of four identically designed elastic spacers 148 the capacitive sensor element 130 appropriate. Each of the four elastic spacers 148 , which are made of an electrically non-conductive PET, is designed to be a cross member 150 having an upper surface and a lower surface, both of which are substantially parallel to the upper surface 140 the electrically insulating carrier element 138 are arranged. The lower surface is arranged to be the electrically insulating support member 138 has. In each case an electrically conductive bridging element 146 is fixed to the lower surface of the cross element 150 of each elastic spacer 148 appropriate. Furthermore, each elastic spacer element comprises 148 an approach 152 each integrally at each end of the cross member 150 is formed and perpendicular to the cross member 150 to the electrically insulating carrier element 138 protrudes. An approach 152 from each elastic spacer 148 is by an adhesive on the second electrically conductive antenna element 134 appropriate, and the other approach 152 of each elastic spacer 148 is at the third electrically conductive antenna element 136 appropriate.

As in 3b is shown for a mechanically unloaded state in which no external force in the specified direction 54 is applied, is each of the electrically conductive bridging elements 146 in spaced relation to the first electrically conductive antenna element 132 to the second electrically conductive antenna element 134 and to the third electrically conductive antenna element 136 arranged.

The elastic spacers 148 have elastic mechanical properties in the specified direction 54 and are able to be reversibly deflected when an external force in the specified direction 54 is applied. If a mechanical load F in the specified direction 54 on the capacitive sensor element 130 is applied, at least one of the electrically conductive bridging elements approaches 146 the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 ,

As long as the mechanical load F that in the specified direction 54 on the capacitive sensor element 130 is applied, below a predetermined value for the mechanical load F which is substantially below a mechanical load F by an electrical device placed on the seat or by an ISOFIX child restraint seat on the vehicle seat 10 is applied, remain the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 galvanically isolated from each other. At this condition of mechanical load F is the first electrically conductive antenna element 132 that with the capacitance measurement circuit 20 is connected, the only sensing part of capacitive sensor element 130 , An electronic device or, if the bridging elements 146 are suitably arranged, an empty ISOFIX CRS grounded, for example, on a vehicle body and on the seat cushion 12 of the vehicle seat 10 is positioned, causes a mechanical load F on the bridging elements 146 that fall under this condition. Thus, the output signal remains out of the capacitance measuring circuit 20 that is a capacitance of the capacitive sensor element 130 below the lower of the two predetermined thresholds, and the evaluation unit 26 generates an output signal 28 that indicates the seat occupancy classification "empty".

Once the mechanical load F that in the specified direction 54 on the capacitive sensor element 130 is applied, equal to or greater than the predetermined value for the mechanical load F is what happens then when a child is sitting on a child seat or an adult on the seat pad 12 is positioned by the electrically conductive bridging elements 146 at least one galvanic contact between the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 provided. This situation is in the 4a and 4b illustrated. In this way, the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 galvanic with the capacitance measuring circuit 20 connected, as well as the first electrically conductive antenna element 132 ,

At this condition of mechanical load F become the first electrically conductive antenna element 132 , the second electrically conductive antenna element 134 and the third electrically conductive antenna element 136 to sensing parts of the capacitive sensor element 130 , Thus, if the vehicle seat 10 occupied by the child on the child seat, the output signal from the capacitance measuring circuit 20 that is a capacitance of the capacitive sensor element 130 , above the lower of the two predetermined threshold values and below the larger of the two predetermined threshold values, and the evaluation unit 26 generates an output signal 28 showing the seat occupancy classification "child". Further, if the vehicle seat 10 occupied by the adult, the output signal from the capacitance measuring circuit 20 that is a capacitance of the capacitive sensor element 130 indicates, above the upper of the two predetermined threshold values, and the evaluation unit 26 generates an output signal 28 showing the seat occupancy ranking "adult".

In this particular embodiment, as in 4a is shown, it is the cross element 150 , which is designed for application of the mechanical load F in the specified direction 54 to be distracted. However, in other embodiments, the approaches are also contemplated 152 the elastic spacer element 148 to configure it under the action of the mechanical load F be deflected, or both the cross element 150 as well as the approaches 152 to be configured to withstand the application of mechanical load F in the specified direction 54 to get distracted.

An alternative embodiment of a capacitive sensor element according to the invention is shown schematically in a plan view in FIG 5 illustrated.

The capacitive sensor element 230 comprises a first electrically conductive antenna element 232 and several, e.g. B. sixteen, second electrically conductive antenna elements 234 , The first electrically conductive antenna element 232 and the second electrically conductive antenna element 234 the plurality of second electrically conductive antenna elements 234 have a planar design and are on a planar surface of an electrically insulating support element 238 arranged and attached to this. It should be noted that the number of sixteen second electrically conductive antenna elements 234 only as a specific example, and that in other embodiments, the number of second electrically conductive antenna elements 234 three or one hundred or any other suitable number.

The first electrically conductive antenna element 232 is formed by a narrow (in comparison to a lateral extent of the electrically conductive antenna element) metal strip which is meandering shaped and two terminals 244 at the ends of the meander through which it connects electrically to the capacitance measuring circuit 20 in an identical way as in 1 for the first embodiment of the capacitive sensor element 130 shown, is connectable. One of the connection terminals 244 is at the meandering portion of the first electrically conductive antenna element 232 via a passage in the electrically insulating support element 238 connected. Along a middle section, the first electrically conductive antenna element comprises 232 four pairs of stubs 60 which extend vertically and coplanar. The second electrically conductive antenna elements 234 the plurality of sixteen second electrically conductive antenna elements 234 are identically formed as rectangular pieces of sheet metal, are arranged in a plane and adjacent to the first electrically conductive antenna element 232 arranged. The plurality of sixteen second electrically conductive antenna elements 234 are contiguous in an arrangement of 4x4 arranged, resulting in a compact installation surface of the capacitive sensor element 230 leads.

In a mechanically unloaded state, the first electrically conductive antenna element 232 and the plurality of sixteen second electrically conductive antenna elements 234 no galvanic connection with each other.

The first electrically conductive antenna element 232 and the plurality of second electrically conductive antenna elements 234 be easily by applying an electrically conductive material to an upper surface 240 the electrically insulating carrier element 238 formed as an electrically insulating substrate, which is designed as a polyethylene terephthalate (PET) layer. The bottom surface of the electrically insulating support member 238 is equipped with an electroconductive layer applied on the PET layer and designed as a protective electrode 242 to serve. The electrically conductive material of the antenna element and / or the guard electrode, for. As a metal or a graphite material or an electrically conductive polymer, z. By printing, deposition, laminating or any other suitable deposition technique on the substrate.

The protection electrode 242 is disposed proximally and from the first electrically conductive antenna element 232 and the plurality of second electrically conductive antenna elements 234 isolated. The electrically conductive protection electrode 242 overlaps in the specified direction 54 Towards the upper surface 240 the electrically insulating carrier element 238 and disposed perpendicularly to it, substantially the region of one of the first electrically conductive antenna element 232 and the plurality of second electrically conductive antenna elements 234 is enclosed.

In addition, the capacitive sensor element comprises 230 several electrically conductive bridging elements 246 each of which is arranged to be the first electrically conductive antenna element 232 and a second electrically conductive antenna element 234 from the plurality of second electrically conductive antenna elements 234 in the specified direction 54 partially overlapped.

Each of the electrically conductive bridging elements 246 is similar to the electrically conductive bridging elements 146 the first embodiment of the capacitive sensor element 130 designed. Each of the electrically conductive bridging elements 246 is fixed to an elastic spacer 248 of several elastic spacers 248 the capacitive sensor element 230 appropriate. Each of the elastic spacers 248 is identical to the elastic spacer elements 148 the first embodiment of the capacitive sensor element 130 formed and has elastic mechanical properties in the specified direction 54 ,

The electrically conductive bridging elements 246 are fixed to the elastic spacers 248 attached, as is the case for the first embodiment of the capacitive sensor element 130 is described.

The first electrically conductive antenna element 232 and a specific one of the plurality of second electrically conductive antenna elements 234 partially formed by a specific one of the plurality of electrically conductive bridging elements 246 are overlapped, remain galvanically isolated from each other when a mechanical load F which is less than a specific predetermined value for the mechanical load F is, in the specified direction 54 to the specific one of the multiple elastic spacers 248 is applied, to which the specific one of the plurality of electrically conductive bridging elements 246 firmly attached. At this condition of mechanical load F is the first electrically conductive antenna element 232 the only sensing part of the capacitive sensor element 230 ,

If a mechanical load F in the specified direction 54 on the capacitive sensor element 230 is applied, at least one of the plurality of electrically conductive bridging elements 246 approaches the first electrically conductive antenna element 232 and one of the plurality of second electrically conductive antenna elements 234 ,

The section of the mechanical load F that is specific to one of the several elastic spacers 248 is applied, leads to an individual surface pressure. For example, the mechanical load F a non-homogeneous space distribution perpendicular to the specified direction 54 to have.

If a mechanical load F is equal to or greater than the specified predetermined value for the mechanical load F in the specified direction 54 to the specific one of the multiple elastic spacers 248 is applied, to which the specific one of the plurality of electrically conductive bridging elements 246 is fixed, the specific one of the plurality of electrically conductive bridging elements 246 at least one galvanic contact between the first electrically conductive antenna element 232 and the specific one of the plurality of second electrically conductive antenna elements 234 that it partially overlaps, ready. At this condition of mechanical load F become the first electric conductive antenna element 232 and the specific one of the plurality of second electrically conductive antenna elements 234, sensing portions of the capacitive sensing element 230 , The more galvanic contacts between the first electrically conductive antenna element 232 and the plurality of second electrically conductive antenna elements 234 are provided, the larger the output of the capacitance measuring circuit 20 ,

• - der Oberflächendruck ist geringer als irgendein spezifischer vorbestimmter Wert für die elastischen Abstandselemente 248, das erste elektrisch leitende Antennenelement 232 ist das einzige Fühlteil (links);
• - der Oberflächendruck ist größer als irgendein spezifischer vorbestimmter Wert für die elastischen Abstandselemente 248, das erste elektrisch leitende Antennenelement 232 und die mehreren zweiten elektrisch leitenden Antennenelemente 234 sind Fühlteile (Mitte); und
• - der Oberflächendruck ist größer als spezifische vorbestimmte Werte von drei der elastischen Abstandselemente 248, das erste elektrisch leitende Antennenelement 232 und die hervorgehobenen drei zweiten elektrisch leitenden Antennenelemente 234 sind Fühlteile des kapazitiven Sensorelements 230 (rechts).

6 shows schematically sensing parts of the capacitive sensor element 230 in three different mechanical load situations:

• the surface pressure is less than any specific predetermined value for the elastic spacers 248 , the first electrically conductive antenna element 232 is the only part of feeling (left);
• the surface pressure is greater than any specific predetermined value for the elastic spacers 248 , the first electrically conductive antenna element 232 and the plurality of second electrically conductive antenna elements 234 are feeler parts (middle); and
• the surface pressure is greater than specific predetermined values of three of the elastic spacers 248 , the first electrically conductive antenna element 232 and the highlighted three second electrically conductive antenna elements 234 are sensing parts of the capacitive sensor element 230 (right).

The specific predetermined surface pressure values for providing at least one galvanic contact between the first electrically conductive antenna element 232 and a specific one of the plurality of second electrically conductive antenna elements 234 that partially overlap it, may be the same or may differ from each other, depending on a desired sensor response, for an expected space distribution of the applied mechanical load F can be specific.

The 7 and 8th 12 schematically illustrate the difference in activation of sensing elements of the capacitive sensing element between a seat occupied by an ISOFIX CRS and a seat occupied by a buckled CRS. Strapped CRS's are normally not grounded, so they have a small capacity. However, they are heavy and activate some or all of the bridging elements. This is schematically in 8th illustrated.

By contrast, ISOFIX CRS can have a high capacity due to grounding, but they are secured by the ISOFIX hooks, so they have a low weight distribution and cause bridging only by some of the bridging elements. This is schematically in 7 illustrates where the mechanical installation surface of the ISOFIX CRS is shown as a dotted surface.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary, and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations of the disclosed embodiments may be understood and appreciated by those skilled in the art to practice the claimed invention, through the study of the drawings, the disclosure, and the appended claims. In the claims, the word "having" or "comprising" does not exclude other elements or steps, and the indefinite article "a," "an," or "an" does not exclude a majority. The mere fact that certain measures are listed in differing sub-claims does not indicate that a combination of these measures can not be used to advantage. Neither of the reference signs in the claims is intended to be construed as limiting the scope of protection.

LIST OF REFERENCE NUMBERS

10

vehicle seat

12

seat cushion

14

A surface-

16

backrest

18

Vehicle seat occupant detection and classification device

20

Capacity measurement circuit

22

Signal generation unit

24

sensing circuit

26

evaluation

28

output

30

capacitive sensor element

32

first electrically conductive antenna element

34

second electrically conductive antenna element

36

third electrically conductive antenna element

38

electrically insulating carrier element

40

upper surface

42

guard electrode

44

terminal

46

electrically conductive bridging element

48

elastic spacer

50

crossmember

52

approach

54

specified direction

56

CAN communication link

58

Airbag control unit

60

stub

F

mechanical load

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7180306 B2 [0006]
• US 2002/0038947 A1 [0007]
• EP 2062789 A1 [0008]

Cited non-patent literature

• J. Smith et al., Electric field sensing for graphical interfaces, IEEE Comput. Graph. Appl., 18 (3): 54-60, 1998 [0028]

Claims (11)

A capacitive sensing element (130) of a vehicle seat occupant detection and classification device (18), the capacitive sensing element (130) comprising: a first electrically conductive antenna element (132) which can be electrically connected to a capacitance measuring circuit (20) for determining a capacitance of the capacitive sensor element (130), at least one second electrically conductive antenna element (134), which is arranged without galvanic connection to one another adjacent to the first electrically conductive antenna element (132), at least one electrically conductive bridging element (146) which is arranged such that it partially overlaps in a specified direction (54) the first electrically conductive antenna element (132) and the second electrically conductive antenna element (134), at least one elastic spacer element (148) having elastic mechanical properties at least in the specified direction (54), wherein the at least one electrically conductive bridging element (146) is fixedly attached to the at least one elastic spacer element (148), wherein the first electrically conductive antenna element (132) and the second electrically conductive antenna element (134) remain galvanically separated from each other when a mechanical load (F) smaller than a predetermined value for the mechanical load (F) is in the specified direction (54) is applied to the capacitive sensor element (130), and wherein the at least one electrically conductive bridging element (146) provides at least galvanic contact between the first electrically conductive antenna element (132) and the second electrically conductive antenna element (134) when a mechanical load (F) equal to or greater than the predetermined one Value for the mechanical load (F) is applied in the specified direction (54) to the capacitive sensor element (130). Capacitive sensor element (130) according to Claim 1 wherein at least one of the first electrically conductive antenna element (132) and the second electrically conductive antenna element (134) has a planar configuration and is disposed on and attached to a planar surface (140) of an electrically insulating support member (138). Capacitive sensor element (130) according to Claim 1 or 2 wherein at least one of the first electrically conductive antenna element (132) and the second electrically conductive antenna element (134) is formed as an electrically conductive strip fixedly mounted on a surface of an electrically insulating substrate. The capacitive sensor element (130) of any one of the preceding claims, wherein a region enclosed by the second electrically conductive antenna element (134) comprises a region enclosed by the first electrically conductive antenna element (132). The capacitive sensor element (130) of any one of the preceding claims, further comprising a third electrically conductive antenna element (136) disposed adjacent to the first electrically conductive antenna element (132) and the second electrically conductive antenna element without galvanic connection the first electrically conductive antenna element (132) forms a single loop, a region enclosed by the second electrically conductive antenna element (134) includes a region enclosed by the first electrically conductive antenna element (132), a region enclosed by the first electrically conductive antenna element (132) includes a region enclosed by the third electrically conductive antenna element (136), and wherein the first electrically conductive antenna element (132) and the third electrically conductive antenna element (136) remain galvanically separated from each other when a mechanical load (F) smaller than the predetermined value for the mechanical load (F) is in the specified direction (54) is applied to the capacitive sensor element (130), and wherein the at least one electrically conductive bridging element (146) provides at least galvanic contact between the first electrically conductive antenna element (132) and the third electrically conductive antenna element (136) when a mechanical load (F) equal to or greater than the predetermined one Value for the mechanical load (F) is applied in the specified direction (54) to the capacitive sensor element (130). Capacitive sensor element (230) according to one of Claims 1 to 3 comprising - a plurality of second electrically conductive antenna elements (234) arranged in a plane and arranged adjacent to the first electrically conductive antenna element (232) without galvanic connection with each other and without galvanic connection to the first electrically conductive antenna element (232), - a plurality electrically conductive bridging elements (246) each arranged to partially overlap the first electrically conductive antenna element (232) and at least one of the plurality of second electrically conductive antenna elements (234) in the specified direction (54), - a plurality of elastic spacers (248) having elastic mechanical properties at least in the specified direction (54), wherein each of the plurality of electrically conductive bridging elements (246) is fixedly attached to one of the plurality of elastic spacers (248), the first electrically conductive antenna element (232) and a specific one of the plurality of second electrically conductive antenna elements (234) partially formed by a specific one of the plurality of electrically conductive bridging elements (246) are left electrically isolated from each other when a mechanical load (F) smaller than a specific predetermined value for the mechanical load (F) in the specified direction (54) is applied to the specific one of the plurality of elastic spacers (248) to which the specific one of the plurality of electrically conductive bridging elements (246) is fixedly mounted, and wherein the specific one of the plurality of electrically conductive bridging elements (246) at least one galvanic contact between the first electric h conductive antenna element (232) and the specific one of the plurality of second electrically conductive antenna elements (234) partially overlapping it provides when a mechanical load (F) equal to or greater than the specific predetermined value for the mechanical load (F ) is applied in the specified direction (54) to the specific one of the plurality of elastic spacers (248) to which the specific one of the plurality of electrically conductive bridging elements (246) is fixedly attached. The capacitive sensor element (130; 230) of any one of the preceding claims, further comprising an electrically conductive guard electrode (142; 242) proximal to the first electrically conductive antenna element (132; 232), the second electrically conductive antenna element, or the plurality of second electrically conductive ones Antenna elements (134; 234) and, if applicable, the third electrically conductive antenna element (136) and are mutually galvanically isolated from each other, wherein the electrically conductive protection electrode (142; 242) in the specified direction (54) substantially overlaps the region framed by one of the first electrically conductive antenna element (132; 232), the second electrically conductive antenna element or the plurality of second electrically conductive antenna elements (134; 234) and, if applicable, the third electrically conductive antenna element (136). A vehicle seat occupant detection and classification device (18) comprising - at least one capacitive sensor element (130; 230) according to any one of Claims 1 to 7 - a capacitance measuring circuit (20) for determining a capacitance of the capacitive sensor element (130; 230), and - an evaluation unit (26) which is configured to receive an output signal from the capacitance measuring circuit (20) and a seat occupant classification based on a level of the received output signal and at least a predetermined threshold value of the output signal. A vehicle seat (10) comprising a seat structure for erecting the vehicle seat (10) on a floor of a passenger compartment of the vehicle, a seat cushion (12) having at least one seat foam element, a seat base supported by the seat structure and adapted to seat the seat cushion (10). 12), the seat base and seat cushion (12) being adapted to support a buttocks of a seat occupant, a seat back (16) provided to support a seat occupant's back, and a vehicle seat occupant detection and classification system (18 ) to Claim 8 , Use of the vehicle seat occupant detection and classification device (18) according to Claim 8 in a vehicle seat (10) comprising a seat base adapted to receive a seat cushion (12) having at least one seat foam member, the seat base and seat cushion (12) being for supporting a seat occupant's buttocks, and a seat back (16) provided for supporting a back of the seat occupant, wherein the at least one capacitive sensor element (30) is disposed on one of the seat cushion (12) or the seat back (16). Use of the capacitive sensor element (130; 230) according to one of Claims 1 to 7 in a vehicle seat occupant recognition and classification device (18) Claim 8 ,

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